In various photonic circuit elements, such as switches, modulators, and Variable Optical Attenuators (VOA), input optical signals are split and/or combined to produce various output optical signals of desired amplitudes. Extinction of an optical signal may occur by splitting an input optical signal into two signals and combining the two signals to interfere with one another so that an output optical signal has a reduced amplitude from that of the input optical signal. An extinction ratio (re) can be calculated based on the relative amplitude of the output optical signal to the input optical signal, which may be presented as a fraction, a percentage, or in decibels based on the amplitudes of the inputs and outputs (e.g., re=Aoutput/Ainput). In several photonic circuits, it is desirable to produce an output signal such that re is below a threshold, so that downstream circuit elements are not inadvertently activated and so that carrier waves are suppressed for signal analysis.
To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures. It is contemplated that elements disclosed in one embodiment may be beneficially utilized on other embodiments without specific recitation.